Portable sheet metal bending brakes are commonly used in the home construction industry for the formation of aluminum sheet metal siding panels. Bending brakes of this type are typically portable so that individual panels may be formed on site. Primarily, the brakes are used to form corner bends in the aluminum sheets which are typically 90-degree angles. As the bend is formed, the sheet metal on either side of the angled bend is flat and straight. There is a need in the home construction industry, however, for the capacity to form curved bends in the sheet metal, such as may be required to form rain gutters or decorative crown molding strips.
The closest patent prior art of which the applicant is aware is U.S. Pat. No. 2,767,762 issued to Peterson on Oct. 23, 1956. This patent discloses an attachment for sheet metal bending brakes which enables the brake to form rounded bends in sheet metal by the use of a die which is rigidly clamped to the frame of the brake. A hinged pressing member is bolted to the jaw of the brake. After the sheet metal piece is firmly clamped between the jaws, the hinged member is pulled down over the top of the sheet which is thereby pressed against the curved surface of the die, thus forming a curved bend in the sheet.
While the Peterson device may be used to form curved bends in a metal sheet, the jaw must be modified to carry the bolted-on hinged pressing member and, similarly, the frame must be modified to carry the clamped die. The Peterson attachment may be disassembled and unbolted between uses, but its attachment and removal is time-consuming and cumbersome. Furthermore, the entire weight of the hinged pressing member is continuously carried by the movable top jaw which makes it cumbersome to use. Finally, because the Peterson pressing member pivots on a fixed axis, it only contacts the sheet at one point and there is no direct pressure applied along the surface of the die, making the formation of smooth bends difficult.
U.S. Pat. No. 3,913,370 issued to Break on Oct. 21, 1975 discloses a bending attachment for a portable sheet metal brake in which the attachment enables the operator to enlarge the bending range of the brake. The attachment disclosed in this reference is held to the brake only by the clamping pressure of the jaw while it is being used.
There is therefore a need in the art for a bending brake attachment which may be used to easily form smooth, rounded bends in sheet metal which is easily detachable, may be universally applied to different bending brakes, and which requires no modification to the brake on which it is used.